1. Field of the Invention
The present invention relates to suspension device and, more particularly, to an improved seat suspension device for a bicycle wherein a deformation mean thereof is disposed to a rear side of a seat of the bicycle.
2. Brief Description of the Prior Art
FIG. 1 shows a conventional seat suspension means which includes a first bar 10 fixedly and transversely connected to a top of a seat tube 11 of a bicycle, a second bar 12 connected to a bottom of a seat 13, at least two links 14 pivotally and in parallel connected between a first end of the first bar 10 and a second end of the second bar 12, and a cylinder 15 with a spring 16 mounted thereto connected between a second end of the first bar 10 and a first end of the second bar 12. Accordingly, when a shock from a rough road is transmitted to the seat tube 11, the cylinder 15 and the spring 16 are compressed and the seat 13 is lowered to absorb the shock. In order to absorb a large impact applied to the bicycle, the spring 16 has to be a high rate spring which is expensive and has a worse performance to minor and frequent bumps. Furthermore, the stroke of the cylinder 15 has to be short because it is disposed between the seat and the seat tube 11, otherwise the seat tube of a standard bicycle frame must be cut or a total height of the seat and the seat tube will too high. The seat 13 will be lowered along a path of sharp arc and has only a short circumferential length because the short stroke of the cylinder 15, so that a rider could drop from the seat 13 when the suspension device is actuated.
Most of the prior arts that consist of sliders, are taking the load down a single axis, which typically binds because the forces are applied to the sliding surfaces out of plane, which adds friction to the device. This restricts the features or the function of the present suspension devices.
The present invention intends to provide an improved seat suspension device to mitigate and/or obviate the above-mentioned problems.